I did encounter the same thing, I got Hahnel Giga T Pro (the older version), stored away somewhere by my mail, I did a spring cleaning and found this item brand new in the box. Well not new anymore since Pro II is now available. What is the difference by the way?

I happily plug in on and played with it. however, when trying to remove it, my goodness, it got stucked real tight.

I checked my SONY flash 43. it has the release button to unlock for removal, as I remembered.

Then trying so hard to look for the release button, but all i could find the an arrow and lock markings. I have not idea what the marking is meant for.

I tried using more force, but just don't think it is normal. now the unit is still on my cam since last night. Tried to find youtube and google, NO ONE SEEMS to have the problem. or just to few ppl using A77 (or SONY) with Hahnel?